Protective device for telephone-circuits.



G. H. HILL. PROTECTIVE DEVICE FOR TELEPHONE CIRCUITS.

APPLICATION FILED NOV. 13. 1915. 1,267,223. Patented May 21,1918.

Inventor: George H .H il l Hisflttorneg -UNITED STATES PATENT OFFICE.

GEORGE E. BILL, OF SCHEN'ECTADY, NEW YORK, ASSIGNOB- TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

PROTECTIVE DEVICE FOR TELEPHONE-CIRCUITS.

Specification of Letters latent. Patented May 21, 1918.

Application filed November 18, 1915. Serial No. 61,280.

To all whom it may concern: 7

Be it known that I, GEORGE H. HILL, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Protective "DGVlCGS for Telephone-Circuits, of which the following is a specification.

This invention relates to protective devices for telephone circuits, and its object is to prevent the occurrence of accidents due to the crossing of telephone lines by conductors carrying a potential that is dangerous to human life. The practice of using telephone lines for train despatching purposes is quite general and on the increase. The telephone mes are built along the railroad right of way and are frequently supported on the same poles as the high tension transmission hues. Where they are not on the high tension transmission poles, they will be found on the overhead trolley poles, which even in the case of direct current, if of 1200 volts or over, presents dangerous possibilities.

It is customary to bring out telephone jacks from the despatching wires at freqlilient intervals along the right of way, so t at conductors can plug their portable telephones into the despatching circuit. It is clearly impossible actually to prevent or avoid possibility of crosses between high tension circuits and the telephone wires where long parallels exist like the cases above mentioned. It becomes desirable, therefore, to protect the telephone circuit thoroughly in case such crosses *do occur.

My invention aims to accomplish this result by providing a device which will automatically ground the telephone wires and will also interpose a positive barrier at the entrance to the telephone jack so that the telephone plug cannot be inserted. A visual signal may also be given, warning the conductor not to attempt to plug in.

The accompanying drawing is a diagrammatic illustration of one form of my mvention.

The telephone wires 1 are parallel with and below the high tension transmission conductors 2. Branch wires 3 lead from the telephone circuit into the box 4 where they connect with a telephone jack 5. In the wall of the box is an opening 6 through suspends which the conductor or other employee can insert the plug 7 of his portable telephone. Pivoted at 8 inside of the box is a heavy arm 9 grounded at 10 and carrying a shutter 11 which is adapted to close the opening 6 and obstruct the entrance of the plug 7. The arm is normally 'held in a raised position, with the shutter' out of line with the opening 6, by means which will respond to an abnormally high potential only. I prefer the arrangement shown, in which the arm is by a fuse wire l2'connected to a spark terminal 13. Adjacent to this termi'nal are two other spark terminals 14, 15 connected respectively with the two sides of the telephone circuit. On the arm is a contact plate 16 adapted to cooperate with contacts 17 on the branch wires from the telephone circuit.

The operation is as follows: The spark gap is set to remain inactive at ordinary telephone voltages, but to spark over at any voltage which may be dangerous. In case a light cross occurs between the telephone line and a high potential wire, the spark gaps will are over and thus ground the telephone wires. If the cross is maintained and the voltage imparted to the telephone wires is suflicient, a considerable amount of energy will pass throu h the fuse wire and in time it will melt an permit the heavy arm 9 to drop by gravity. Obviously, the time required to effect this result will depend upon the voltage impressed, and the size of the fuse. When the arm: drops, the contact plate 16 closes upon the contacts 17 and makes a solid ground for the telephone wires. At the same time, the shutter on the arm passes down in front of the jack and obstructs the opening 6, so that a telephone plug cannot be inserted. The shutter will be "plainly visible through the opening, so that 2. The combination with a telephone line, of a jack connected thereto, a movable member for ounding said line and obstructing said jac a fuse keeping said member inoperative, and a spark gap in circuit with said fuse.

3. The combination with a, telephone line, of a jack connected thereto, a shutter adapted to obstruct said jack, and means resp0n sive to a dangerous voltage on said line for causing said shutter to move in front of said jack.

4. The combination with a telephone line, of a jack connected thereto, a member mounted adjacent to said jack and arranged to obstruct the same a fuse holding said member out of obstructing position, and a spark gap in circuit with said fuse.

5. The combination with a telephone line, of a jack connected thereto, a grounded arm pivoted adjacent to said jack and rovided with means for obstructing said jac a fuse holding said arm in inoperative position with reference to said jack, a spark ga in circuit with said fuse, and contacts for s ort circuiting the jack when the fuse melts and the arm moves to operative position.

In witness whereof I'have hereunto set my hand this 11th day of November, 1915. GEORGE H. HILL. 

